mRNA sequence data of three powdery mildew fungi - GcM3, OnM2 and GcC1 (mycelia and haustoria containing infected plant leaves)

Powdery mildew (PM) is one of the most important and widespread plant diseases caused by obligate biotrophic Ascomycete fungi in the order of Erysiphales. Monocot PM fungi such as Blumeria graminis f.sp. hordei (Bgh) infectious on barley and B. graminis f.sp. tritici (Bgt) infectious on wheat exhibit high-level of host-specialization. By contrast, many dicot PM fungi display rather broad host ranges. To understand why different PM fungi adopt distinct modes of host-adaption, we sequenced the genomes of four dicot PM strains belonging to Golovinomyces cichoracearum (GcC1, GcM1, GcM3) or Oidium neolycopersici (OnM2) and conducted comparative sequence analyses. PM fungi have highly repetitive genomes that are difficult to perform gene prediction. By combing RNA-seq expression evidence with ab initio gene prediction, we successfully improved the number of predicted genes from 4000 to 6000. By comparing the transcriptional profiling from haustoria with mycelia in OnM2 and GcM3, we found that 86%-96% of the predicted genes are expressed in mycelia and/or haustoria, indicating an efficient expression system of PM fungi. Besides, our results showed that gene regulation mechanisms in haustorial cells maybe under gone a much higher level of diversification between OnM2 and GcM3, since they share only a small proportion (21%) of genes up-regulated in huastoria cells. Notably, a higher proportion of candidate effector genes are selectively up-regulated in haustorial cells, agreeing with their function in suppressing host defense and facilitating nutrient uptake. Overall design: This RNA-seq data set contains the transcriptional profiling from mycelia of two powdery mildew biotypes, as well as transcriptional profiling of haustoria containing plant leaves at 6 dpi. Haustoria containing samples were collected in three replicates, whereas only one replicate was collected for mycelia sample. Pair-end 101bp RNA-seq was performed on all samples. Libraries were prepared using Illumina TruSeq RNA Sample Preparation Kit v2. Fragments were selected for sequencing on Illumina HiSeq1500 at the UM-IBBR Sequencing Core at the University of Maryland.